In the recent processes for production of semiconductor devices, the importance of processing techniques for density enhancement and micronization is ever increasing. As one of such processing techniques, a chemical mechanical polishing (CMP) technique is an essential technique for formation of shallow trench isolation (STI), the flattening of pre-metal insulating films or interlayer insulating films, formation of plugs, and formation of embedded metal wirings, for example, in a process for producing semiconductor devices.
Most commonly used as a CMP polishing liquid is a silica-based CMP polishing liquid containing silica (silicon oxide) particles such as fumed silica or colloidal silica as abrasive particles. A feature of the silica-based CMP polishing liquid is its high versatility, and a wide range of types of films regardless of whether it is an insulating film or a conductive film can be polished when the content of abrasive particles, pH, and additives, for example, are appropriately selected.
Meanwhile, there is a growing demand for a CMP polishing liquid containing cerium compound particles as abrasive particles to be used mainly for insulating films such as silicon oxide films. For example, with a cerium oxide-based CMP polishing liquid containing cerium oxide (ceria) particles as abrasive particles, even if the content of abrasive particles is smaller than that of the silica-based CMP polishing liquid, a silicon oxide film can be polished at a high rate (e.g., see Patent Literatures 1 and 2 below).
In addition, a CMP polishing liquid using tetravalent metal element hydroxide particles as abrasive particles has been studied and a technique thereof is disclosed in Patent Literature 3 below. This technique takes advantage of a chemical action of the tetravalent metal element hydroxide particles and minimizes a mechanical action, thereby achieving a decrease in polishing scratches caused by the abrasive particles and an increase in polishing rate at the same time.